Noise is sufficiently reduced in a moving image.A determination section determines, each time an input image is input, whether a change amount of a pixel value distribution in the input image and an output image that is output is smaller than a predetermined threshold value. A mixing ratio supply section supplies a value that becomes larger as the number of times the change amount is sequentially determined to be smaller than the predetermined threshold value becomes larger, the value serving as a mixing ratio of the output image in mixing of the input image and the output image. A mixing section mixes, each time the input image is input, the input image and the output image based on the supplied mixing ratio and outputs the input image and the output image to serve as a new output image.